1. Field of the Invention
The present invention relates to hydraulic presses that have very large working surfaces for pressing and forming sheets which are resting on a forming tool. More specifically, the present invention relates to the mechanism used for applying the compressive force to an elastic pad which then acts to press the sheets against the forming tool.
2. Description of the Prior Art
In hitherto known presses, very large working surfaces have been utilized to form or mold sheets of various materials on a suitable forming tool. This forming has been achieved by pressing the sheets against the forming tools by means of a forming pad of elastic material. The compressive force is achieved by use of a pressure medium which is pumped into a pressure cell with a bag-like diaphragm located above the press pad. The diaphragm is formed with an annular bead around an opening and is secured between two attachment members, at least one of them being annular in shape. These attachment members form an annular slot fitting the shape of the diaphragm bead. The pressure medium space is then defined by the inner surface of the diaphragm and the attachment members. Tools with workpieces are placed in a recess in a trough-like supporting member which can be displaced between a position outside the press and a pressing position inside the press. At the end wall, defining the pressure cell space, there is a vertically movable metallic sealing strip which, during pressing, is pressed downwards towards an end piece wall in the trough-like supporting member for tools and workpieces, thus bridging an unavoidable gap between these end walls and preventing the press pad from being pressed out through the gap.
In presses of hitherto known designs, the diaphragm at the end pieces of the press has been subjected to movements and forces when filling the pressure cell, involving leakage and tendencies of withdrawal of the diaphragm bead from the slot for this bead formed by the attachment members.
The present invention substantially eliminates these harmful movements and forces and improves the mode of operation of the press, the sealing ability of the diaphragm attachment and the life of the diaphragm.